From b4dcae20ccc5189bb8102693af7ae00b74b050be Mon Sep 17 00:00:00 2001
From: "Louis R. Marascio" <marascio@gmail.com>
Date: Wed, 22 Sep 2021 11:39:23 -0500
Subject: [PATCH] Add option `MSGPACK_BUILD_DOCS`.

This option explicitly controls the generation of targets related to
Doxygen generation, rather than relying solely on whether Doxygen is
discovered.

It is enabled by default to preserve existing behavior, but if disabled
then no Doxygen targets will be generated. This is useful when the
library is included via CMake's `add_subdirectory()`.
---
 CMakeLists.txt | 41 ++++++++++++++++++++++-------------------
 1 file changed, 22 insertions(+), 19 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 916e40eb..102fadbe 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -24,6 +24,7 @@ OPTION (MSGPACK_CXX20 "Using c++20 compiler" OFF)
 OPTION (MSGPACK_32BIT            "32bit compile"                        OFF)
 OPTION (MSGPACK_USE_X3_PARSE     "Use Boost X3 parse"                   OFF)
 OPTION (MSGPACK_BUILD_TESTS      "Build tests"                          OFF)
+OPTION (MSGPACK_BUILD_DOCS       "Build Doxygen documentation"          ON)
 OPTION (MSGPACK_FUZZ_REGRESSION  "Enable regression testing"            OFF)
 OPTION (MSGPACK_BUILD_EXAMPLES   "Build msgpack examples"               OFF)
 OPTION (MSGPACK_GEN_COVERAGE     "Generate coverage report"             OFF)
@@ -153,28 +154,30 @@ IF (MSGPACK_BUILD_EXAMPLES)
 ENDIF ()
 
 # Doxygen
-FIND_PACKAGE (Doxygen)
-IF (DOXYGEN_FOUND)
-    LIST (APPEND Doxyfile_cpp_CONTENT
-        COMMAND ${CMAKE_COMMAND} -E copy ${CMAKE_CURRENT_SOURCE_DIR}/Doxyfile ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile_cpp
-        COMMAND ${CMAKE_COMMAND} -E echo "FILE_PATTERNS      = *.hpp" >> ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile_cpp
-        COMMAND ${CMAKE_COMMAND} -E echo "OUTPUT_DIRECTORY   = doc_cpp" >> ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile_cpp
-        COMMAND ${CMAKE_COMMAND} -E echo "INPUT              = ${CMAKE_CURRENT_SOURCE_DIR}/include" >> ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile_cpp
-        COMMAND ${CMAKE_COMMAND} -E echo "EXTRACT_ALL        = YES" >> ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile_cpp
-        COMMAND ${CMAKE_COMMAND} -E echo "STRIP_FROM_PATH    = ${CMAKE_CURRENT_SOURCE_DIR}/include" >> ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile_cpp
-    )
-    IF (DOXYGEN_DOT_FOUND)
+IF (MSGPACK_BUILD_DOCS)
+    FIND_PACKAGE (Doxygen)
+    IF (DOXYGEN_FOUND)
         LIST (APPEND Doxyfile_cpp_CONTENT
-            COMMAND ${CMAKE_COMMAND} -E echo "HAVE_DOT       = YES" >> ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile_cpp
+            COMMAND ${CMAKE_COMMAND} -E copy ${CMAKE_CURRENT_SOURCE_DIR}/Doxyfile ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile_cpp
+            COMMAND ${CMAKE_COMMAND} -E echo "FILE_PATTERNS      = *.hpp" >> ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile_cpp
+            COMMAND ${CMAKE_COMMAND} -E echo "OUTPUT_DIRECTORY   = doc_cpp" >> ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile_cpp
+            COMMAND ${CMAKE_COMMAND} -E echo "INPUT              = ${CMAKE_CURRENT_SOURCE_DIR}/include" >> ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile_cpp
+            COMMAND ${CMAKE_COMMAND} -E echo "EXTRACT_ALL        = YES" >> ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile_cpp
+            COMMAND ${CMAKE_COMMAND} -E echo "STRIP_FROM_PATH    = ${CMAKE_CURRENT_SOURCE_DIR}/include" >> ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile_cpp
+        )
+        IF (DOXYGEN_DOT_FOUND)
+            LIST (APPEND Doxyfile_cpp_CONTENT
+                COMMAND ${CMAKE_COMMAND} -E echo "HAVE_DOT       = YES" >> ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile_cpp
+            )
+        ENDIF ()
+        ADD_CUSTOM_TARGET (
+            doxygen
+            ${Doxyfile_cpp_CONTENT}
+            COMMAND ${CMAKE_COMMAND} -E echo "PROJECT_NAME       = \"MessagePack for C++\"" >> ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile_cpp
+            COMMAND ${DOXYGEN_EXECUTABLE} ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile_cpp
+            VERBATIM
         )
     ENDIF ()
-    ADD_CUSTOM_TARGET (
-        doxygen
-        ${Doxyfile_cpp_CONTENT}
-        COMMAND ${CMAKE_COMMAND} -E echo "PROJECT_NAME       = \"MessagePack for C++\"" >> ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile_cpp
-        COMMAND ${DOXYGEN_EXECUTABLE} ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile_cpp
-        VERBATIM
-    )
 ENDIF ()
 
 # Install library.